Wednesday, June 20, 2012

Are logical truths empirical?

Anthony mentions in his comments here that he holds that logic itself is empirical, whereas I holds (he believes) that knowledge of logic is innate.

Well, I wouldn't exactly describe my position the way he does. I lean towards the Wittgensteinian position that there are no 'logical truths' as such, but rather principles like the Contradiction and Excluded Middle are built into the 'scaffolding' of our language, so that we can't describe them using language, but only show them, as it were. On the idea that 'logic itself is empirical' – by which I assume he means that logical truths are empirical – I don't know what to say. What does 'empirical' mean? If the idea is absurd, how would we demonstrate its absurdity?

Aristotle discussed the problem in book 4 of the Metaphysics. Aquinas' commentary on it is in the Logic Museum here. It includes links to Aristotle's original text.

11 Comments:

>> I lean towards the Wittgensteinian position that there are no 'logical truths' as such, but rather principles like the Contradiction and Excluded Middle are built into the 'scaffolding' of our language, so that we can't describe them using language, but only show them, as it were.

I'm not familiar with the specifics of this, but it sounds like something which could be correct.

But that doesn't really answer the question of how we learn these truths. It just punts it to the question of how we learn language.

>> What does 'empirical' mean?

My understanding is that it means "a posteriori", which means "known on the basis of experience".

My understanding is that we have "The Empiricism Thesis: We have no source of knowledge in S or for the concepts we use in S other than sense experience." (http://plato.stanford.edu/entries/rationalism-empiricism/)

This would be juxtaposed against the position that knowledge/concepts are innate, and/or that they are intuited. The term intuition, as used against empiricism, would refer to non-sense-based intuition. It is, quite literally, a theory of ESP - extrasensory perception. Intuition as in the subconscious use of induction on patterns observed through the use of our ordinary senses, is not a type of intuition which is opposed to empiricism, at least as I understand the term.

I'm not sure I understand what you guys mean by a 'discontinuity'. I guess I'm trying to answer the question Ed asks in the final paragraph of Is time travel possible? as to whether Dr Who style forward time travel is inconsistent with Locke. My thought is that Dr Who could spend what is to us more than a hundred years whizzing around at close to the speed of light. But he can make this time interval, for himself, as small as he likes by travelling sufficiently close to light speed. He could leave in our 1999 and return in our 2101 and yet, for him, be away for minutes (if he could withstand the accelerations required). This gives a kind of time travel that doesn't involve any discontinuities (except that he will have to wind his clocks on a bit when he returns in 2101) and does not violate Locke's maxim. There might be other kinds of time travel, maybe involving Parfit/Star Trek style disassembly-reassembly, that would be discontinuous. This, I think, is the more interesting question, more for what it says about our idea of self than for what it says about the possibilities of time travel.

Yes, it seems there are three main theories for how we learn the meaning of "yes" and "no. And I must warn you that I can't do justice to the first two, because I find them to be incoherent. So please, point out where I am wrong.

1) We are born with the knowledge of what "yes" and "no" mean.

2) We learn the meaning of "yes" and "no" through extrasensory perception.

3) We learn the meaning of "yes" and "no" by observing patterns.

I find 1 to be absurd. Babies don't come out of the womb understanding the meaning of "yes" and "no".

Against 2, I would say that there is no scientific evidence for extrasensory perception, and that learning is adequately explained without resorting to extrasensory perception.

Something like, observing that things are sometimes white, and sometimes not white, but never white and not-white at the same time? So we conclude that it is never true of any x that it is white and not-white at the same time?

>> Something like, observing that things are sometimes white, and sometimes not white, but never white and not-white at the same time? So we conclude that it is never true of any x that it is white and not-white at the same time?

Well, no, not really.

I'd try to be more specific, but I'm not really sure what your question is.

Logic is an axomatic system that preserves truth from premises to conclusion. That is why one of the central question in philosophy of science is of the nature of induction, which is logically invalid, but, some people claim it is empirically valid. I think the fact that this contention exist all, goes some way to show that logic is not empirical.

when the premises can be scientifically tested, then we have an empirical statement.